The present disclosure relates generally to conveying technologies and particularly to particulate media conveying systems and apparatuses.
Myriad techniques exist to convey particulate media in many different industries. One technique involves pneumatic conveying typically used for bulk solids. These systems may be categorized as vacuum or negative pressure, positive pressure, or a combination of the two. They can be operated in dilute-phase where there is a lot of air and the media moves quickly, or in dense-phase where the media moves slowly or in gulps.
Vacuum systems are limited to a 15 psi pressure differential (absolute vacuum) so they are limited in how hard they can pull the media along, but this technique is by far the most common way to convey pneumatically. Very low bulk density materials will get blown around in even the slightest breeze. Cereals, powders, and grains are also easily moved with vacuum. As the intake is atmospheric, a pick-up wand may be pushed down into the bulk solid and it will get vacuumed up. However, materials with higher bulk density, such as steel shot that is physically dense and aerodynamic, will not convey or convey very slowly. Indeed, a vertical vacuum pipe will have a hard time lifting a heavy and aerodynamic particle because the air just goes around it.
Positive pressure conveying systems are not limited to 15 psi. The media to be conveyed is put into a closed vessel that is subsequently pressurized. The vessel is typically shaped so the pressurized air tries to escape the vessel through the media, pushing the media along.
Screw conveyors are another popular conveying technology. A long pipe has a helical feed wire or screw put down the middle. Turning either the screw (typical) or tube (rare) will cause media to feed up the tube. The tube has a limit to how steep it can be, particularly with free-flowing materials.
Bucket elevators are large and mechanically complex systems where a series of buckets ride along on a pair of chains. The buckets are passed under a pick-up station where media is deposited. The buckets then follow the conveyor, usually upwards and sideways only, to a single drop-off station where the buckets are inverted. Such systems are quite varied. For example, some may be belt driven, employ a continuous belt instead of buckets, manufactured from a variety of different materials, etc.
The vast majority of particulate media conveying systems for shot peening use vacuum conveying or bucket elevators. Vacuum conveying limits these systems to using smaller media, as larger media will not convey up long vertical runs, as discussed above. The bucket elevators are used in machines that may put out hundreds to thousands of pounds of shot per minute. These technologies are both single pick-up and single drop-off. In an effort to overcome the one-source to one-destination shortcoming, these systems stack all their equipment and use gravity to convey between items. Consequently, very tall machines must be employed that have only one flow path the media can follow. Conventional shot peen systems are thus typically enormous, expensive, and limited to conveying media with a single pick-up and drop-off.
Accordingly, novel systems and apparatuses for conveying multiple medias with minimization or elimination of cross-contamination, with multiple pick-up and drop-off locations, and compact size are therefore desired.